Not entirely correct.
The Summit use a complex digital control of the phase of the two woofers so that the radiation pattern of the bass gradually approaches that of the panel as frequency rises towards the crossover point. This meant that at low frequencies, the two woofers are acoustically in phase with each other (and the panel), and at the crossover point, the from woofer is in phase with the panel, and the bottom woofer is acoustically out of phase, thus making the combined output of the two woofers mimic a dipole. Since the second woofer is placed in the bottom and not on the rear of the speaker, I assume that there is a 90 degree phase shift added or subtracted.
